Field of the Invention
The present invention relates to a focus control apparatus, a control method therefor, a storage medium therefor, and an image capturing apparatus.
Description of the Related Art
It is not easy for a photographer to perform precise focus control with respect to a subject by manipulating manual focus (MF manipulation) on a focus control apparatus, such as a high-definition video camera supporting full high-definition, 4K, etc. Especially when performing focus control while checking a viewfinder, a panel, or the like, a slip in focus control may occur that cannot be checked on the viewfinder, the panel, or the like. To correct such a slip in focus control, MF assistance methods are suggested whereby an autofocus (AF) operation is performed after manipulating MF.
Japanese Patent Laid-Open No. 2003-241077 suggests a technique to, after detecting completion of MF manipulation and pressing of a release button or the like, perform only one session of detailed focus control through an AF operation within a minute range.
Japanese Patent Laid-Open No. 2010-97167 suggests a technique whereby a focus detection frame is automatically set to an area in an in-focus state among a plurality of focus detection areas set on a screen (areas targeted for AF), and if a subject moves on the screen afterwards, the subject is automatically tracked by the focus detection frame.
Japanese Patent Laid-Open No. 2007-248615 suggests a technique to display a bar showing an in-focus degree that is calculated while manipulating MF, so as to enable a user to easily check the state of a slip in focus control while manipulating MF.
However, with the technique of Japanese Patent Laid-Open No. 2003-241077, once focus control has been performed through AF, subtle shaking of a subject may bring a captured image slightly out of focus. With the technique of Japanese Patent Laid-Open No. 2010-97167, if a small focus detection frame is set, a moving subject easily deviates from the focus detection frame, thereby giving rise to the possibility that AF cannot be performed appropriately. The technique of Japanese Patent Laid-Open No. 2007-248615 does not take into consideration a case where a focus detection area for calculating an in-focus degree is dynamically changed by, for example, a user's selection; this may disable precise focus control with respect to a desired subject.